Sterling silver is often characterized as pure silver, when in fact it is a silver alloy. Pure silver, also called fine silver, is defined as 99.9% pure silver, but is too soft for most uses. Sterling contains 92.5% silver, with the remaining 7.5% being another metal, most often copper. The addition of the less costly metal - often called a base metal - serves to harden the resulting alloy so that the metal can be cast into shapes that it will retain with use.
Sterling silver is marked with a stamp on the bottom of the piece. The shape of the stamp varies from country to country, and in the US from manufacturer to manufacturer.
One of the most common uses of sterling is in making fine tableware. This typically includes utensils - knives, forks, and spoons - as well as coffee and tea service sets, with silver trays. A set of formal silverware might include several different types of forks which would only be used in the place setting if the meal called for them - a seafood fork, for example, is a tiny, usually three-pronged fork used for oysters, clams, and so on. Spoons can range from the tiny demitasse spoon to the soup spoon, with larger serving spoons completing the collection.
Sterling silver tarnishes simply by being in contact with the air. Pure silver is, like gold, impervious to tarnish, or oxidation on the surface. It is the alloy metal which attracts the tarnish. Rub your thumb over an apparently shiny piece of sterling. You may find a dull smudge on your skin that indicates that the sterling silver is beginning to tarnish.
Your sterling silver can be kept polished simply by buffing with a cotton cloth regularly. Sterling silver that has been stored away unused for a period of time might develop a significant layer of tarnish and need a polishing paste. Before you employ the paste and elbow grease, try the following butler's trick.
Line the bottom of the sink or a dishpan with tin foil, and fill with hot water. Add some salt and baking soda. Proportions aren't critical here, just throw in a couple teaspoons of each. Next, put the silver into the water, with the pieces touching each other and the tin foil. The tarnish will be pulled off the silver to the foil - in cases of heavy tarnish, you will be able to see it flaking off. Leave in for no more than five minutes, rinse and dry.